From patchwork Tue Apr 7 16:50:28 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeffrey Hugo X-Patchwork-Id: 11478435 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 75B55912 for ; Tue, 7 Apr 2020 16:51:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 529E020936 for ; Tue, 7 Apr 2020 16:51:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="XlPer97R" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726602AbgDGQvb (ORCPT ); Tue, 7 Apr 2020 12:51:31 -0400 Received: from mail27.static.mailgun.info ([104.130.122.27]:36139 "EHLO mail27.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726552AbgDGQva (ORCPT ); Tue, 7 Apr 2020 12:51:30 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1586278290; h=References: In-Reply-To: Message-Id: Date: Subject: Cc: To: From: Sender; bh=b1pY8cTgRt+LvatfRduM8QYisMGaxGkElw95LNjYo9I=; b=XlPer97RoTnwcs3PTJM3wXsBQCtqkXFAPbKrUU3C+k23W/SGMDTzRzLJ4cKl4WKZSoMMp6pU KdAQtrN9WwfsiE+WrHZlYpdHetKTG28ITnAur0jUsd1qW6wKREmvJcqe+TOVAkoM/mkhTbIu BFaaQCexCLfQeAl2QuB9n+SMflc= X-Mailgun-Sending-Ip: 104.130.122.27 X-Mailgun-Sid: WyI1MzIzYiIsICJsaW51eC1hcm0tbXNtQHZnZXIua2VybmVsLm9yZyIsICJiZTllNGEiXQ== Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by mxa.mailgun.org with ESMTP id 5e8caf92.7fe15d194490-smtp-out-n05; Tue, 07 Apr 2020 16:51:30 -0000 (UTC) Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 0755DC44788; Tue, 7 Apr 2020 16:51:30 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-caf-mail-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=2.0 tests=ALL_TRUSTED,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.0 Received: from jhugo-perf-lnx.qualcomm.com (i-global254.qualcomm.com [199.106.103.254]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: jhugo) by smtp.codeaurora.org (Postfix) with ESMTPSA id 72B08C433BA; Tue, 7 Apr 2020 16:51:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 72B08C433BA Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=jhugo@codeaurora.org From: Jeffrey Hugo To: manivannan.sadhasivam@linaro.org, hemantk@codeaurora.org Cc: linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, Jeffrey Hugo Subject: [PATCH v2 3/5] bus: mhi: core: Remove link_status() callback Date: Tue, 7 Apr 2020 10:50:28 -0600 Message-Id: <1586278230-29565-4-git-send-email-jhugo@codeaurora.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1586278230-29565-1-git-send-email-jhugo@codeaurora.org> References: <1586278230-29565-1-git-send-email-jhugo@codeaurora.org> Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org If the MHI core detects invalid data due to a PCI read, it calls into the controller via link_status() to double check that the link is infact down. All in all, this is pretty pointless, and racy. There are no good reasons for this, and only drawbacks. Its pointless because chances are, the controller is going to do the same thing to determine if the link is down - attempt a PCI access and compare the result. This does not make the link status decision any smarter. Its racy because its possible that the link was down at the time of the MHI core access, but then recovered before the controller access. In this case, the controller will indicate the link is not down, and the MHI core will precede to use a bad value as the MHI core does not attempt to retry the access. Retrying the access in the MHI core is a bad idea because again, it is racy - what if the link is down again? Furthermore, there may be some higher level state associated with the link status, that is now invalid because the link went down. The only reason why the MHI core could see "invalid" data when doing a PCI access, that is actually valid, is if the register actually contained the PCI spec defined sentinel for an invalid access. In this case, it is arguable that the MHI implementation broken, and should be fixed, not worked around. Therefore, remove the link_status() callback before anyone attempts to implement it. Signed-off-by: Jeffrey Hugo Reviewed-by: Manivannan Sadhasivam --- drivers/bus/mhi/core/init.c | 6 ++---- drivers/bus/mhi/core/main.c | 5 ++--- include/linux/mhi.h | 2 -- 3 files changed, 4 insertions(+), 9 deletions(-) diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c index b38359c..2af08d57 100644 --- a/drivers/bus/mhi/core/init.c +++ b/drivers/bus/mhi/core/init.c @@ -812,10 +812,8 @@ int mhi_register_controller(struct mhi_controller *mhi_cntrl, if (!mhi_cntrl) return -EINVAL; - if (!mhi_cntrl->runtime_get || !mhi_cntrl->runtime_put) - return -EINVAL; - - if (!mhi_cntrl->status_cb || !mhi_cntrl->link_status) + if (!mhi_cntrl->runtime_get || !mhi_cntrl->runtime_put || + !mhi_cntrl->status_cb) return -EINVAL; ret = parse_config(mhi_cntrl, config); diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c index eb4256b..473278b8 100644 --- a/drivers/bus/mhi/core/main.c +++ b/drivers/bus/mhi/core/main.c @@ -20,9 +20,8 @@ int __must_check mhi_read_reg(struct mhi_controller *mhi_cntrl, { u32 tmp = readl(base + offset); - /* If there is any unexpected value, query the link status */ - if (PCI_INVALID_READ(tmp) && - mhi_cntrl->link_status(mhi_cntrl)) + /* If the value is invalid, the link is down */ + if (PCI_INVALID_READ(tmp)) return -EIO; *out = tmp; diff --git a/include/linux/mhi.h b/include/linux/mhi.h index ad19960..be704a4 100644 --- a/include/linux/mhi.h +++ b/include/linux/mhi.h @@ -335,7 +335,6 @@ struct mhi_controller_config { * @syserr_worker: System error worker * @state_event: State change event * @status_cb: CB function to notify power states of the device (required) - * @link_status: CB function to query link status of the device (required) * @wake_get: CB function to assert device wake (optional) * @wake_put: CB function to de-assert device wake (optional) * @wake_toggle: CB function to assert and de-assert device wake (optional) @@ -417,7 +416,6 @@ struct mhi_controller { void (*status_cb)(struct mhi_controller *mhi_cntrl, enum mhi_callback cb); - int (*link_status)(struct mhi_controller *mhi_cntrl); void (*wake_get)(struct mhi_controller *mhi_cntrl, bool override); void (*wake_put)(struct mhi_controller *mhi_cntrl, bool override); void (*wake_toggle)(struct mhi_controller *mhi_cntrl);